The present invention relates to a printing technology in which images are printed with discharged ink droplets.
Ink-jet printers in which ink is discharged from a head are currently being used on a wide scale as computer output devices. In conventional ink-jet printers, each pixel can be reproduced with two values (xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d), and multiple-value printers capable of expressing three or more values with a single pixel have recently been proposed. Multiple-value pixels can, for example, be reproduced by adjusting the size of the dots formed at each pixel position. An arrangement should preferably be adopted in which a plurality of types of drive signals having various waveforms can be fed to the print head in order to be able to form dots having maximum diversity.
However, the recording positions of dots in the main scanning direction do not necessarily coincide when different types of drive signals are used to print a single page, and image quality may be adversely affected accordingly. This problem is not limited to the reproduction of multiple-value pixels and is common to other cases in which a multiple types of drive signals are used within a single page.
An object of the present invention, which was perfected in order to address the above-described problems of the prior art, is to provide a technique that reduces the difference in the recording positions of dots in the main scanning direction when a plurality of types of drive signals are used within a single page.
In order to solve at least part of the above problems, the present invention performs printing with a printing device including: a print head having a plurality of nozzles and a plurality of discharge drive elements for causing the plurality of nozzles to discharge ink droplets from; and a head drive for reshaping a common drive signal in accordance with print signals and supplying drive signals to the discharge drive elements. One of n types of common drive signals is selectively generated for each main scan where n is an integer of 2 or greater. The selected common drive signal is reshaped in accordance with the print signals with respect to each pixel, thereby generating the drive signals to be supplied to the discharge drive elements. Recording positions in the main scanning direction are adjusted with positional difference adjustment values prepared in advance in order to reduce a difference between the recording positions in the main scanning direction, where the positional difference adjustment values are prepared for combinations of common drive signals that are usable within one page of the print medium and that are selected from all possible combinations of common drive signals suitable for use in a forward main scanning pass and common drive signals suitable for use in a reverse main scanning pass.
In this structure, each of the combinations usable within one page of the print medium is adjusted using positional difference adjustment values prepared in advance, making it possible to reduce the difference between the recording positions of dots in the main scanning direction even when multiple types of drive signals are used within one page.
As used above, the phrase xe2x80x9ccommon drive signals suitable for use during a forward main scanning pass, and common drive signals suitable for use during a reverse main scanning passxe2x80x9d is not necessarily premised on performing bi-directional printing and can also be applied to unidirectional printing. In the case of unidirectional printing, this will correspond, for example, to the absence of the portion xe2x80x9ccommon drive signals suitable for use during a reverse main scanning pass.xe2x80x9d
The positional difference adjustment values include bi-directional adjustment values for use during bi-directional printing and/or unidirectional adjustment values for use during unidirectional printing. With this arrangement, the corresponding differences between recording positions can be adjusted in accordance with bi-directional printing, unidirectional printing, or any other printing technique acceptable for use within one page.
When the main scan is performed using at least one specific common drive signal selected from n types of common drive signals, a main scan may be carried out at a main scan speed different from the speed at which the main scan is performed using other common drive signals.
Recording positions can thus be adjusted highly efficiently because positional differences tend to occur particularly readily in the main scanning direction when different main scan speeds are involved.
The print head may be capable of forming multiple types of dots of different sizes on a print medium with the aid of nozzles, and the print signals may be signals with a plurality of bits per pixel that are used for recording each pixel with multi tones. In this case, each of the n types of common drive signals generates a plurality of pulses during a single pixel period, and the drive signals are generated by the reshaping of the common drive signal in accordance with the multi-bit print signals.
In particular, various common drive signals are highly likely to be used in print heads capable of forming dots having different sizes. Consequently, the present invention is particularly effective for reducing the differences in the recording positions of dots in the main scanning direction under such conditions.
The present invention can be implemented as a variety of embodiments, examples of which include printing methods, printing devices, print control methods, print control devices, computer programs for performing the functions of these methods or devices, recording media for storing these computer programs, and data signals embodied in a carrier wave containing these computer programs.